Page 83 - My FlipBook

BONES. 93
inferior and posterior borders, and fits into the pterygoid notch between
the two pterygoid plates of the sphenoid. Posteriorly, this process has
a triangular surface which rounds out the lower portion of the ptery-
goid fossa. The borders of this process are serrated for articulation
with both pterygoid plates of the sphenoid bone.
The Orbital Process extends outwardly from the superior border of
the vertical plate, overhanging its outer surface. This process has five
surfaces, enclosing a cellular cavity, generally opening through its inter-
nal or ethmoidal surface. When it so opens it communicates with the
posterior ethmoidal cells. Sometimes, however, this cell-like cavity
opens through the posterior or sphenoidal surface and communicates
with the sphenoidal sinus, or it may open both ways. Three of these
surfaces—the anterior or maxillary, the posterior or sphenoidal, and the
internal or ethmoidal—are articulating surfaces, while the remaining two,
the superior or orbital and the external or zygomatic, are free.
The Anterior or llaxillary Surface is directed forward, outward, and
downward. It is oblong in form and articulates with the posterior
superior angle of the inner surface of the superior maxilla.
The Posterior or Sphenoidal Surface is directed backward, upward,
and inward, and articulates with the vertical portion of the sphenoidal
turbinated bone.
The Internal or Ethmoidal Surface is directed inward, upward,
and forward, and articulates with the vertical plate of the ethmoid
bone.
The Superior or Orbital Surface is triangular in form, extends up-
ward and outward, and forms the posterior angle of the floor of the
orbit.
The External or Zygomatic Surface is smooth and oblong in form, is
directed outward, backward, and downward, and forms a portion of the
spheno-maxillary fossa.
The Sphenoidal Process curves upward, backward, and inward from
the posterior third of the superior border, and presents three surfaces,
the superior, external, and internal ; and two borders, the anterior and
posterior.
The Superior Surface is the smallest of the three, and articulates with
the horizontal portion of the sphenoidal turbinated bone. It is marked
by a groove which assists in forming the pterygo-palatine canal.
The External Surface is divided into two portions, anterior and pos-
terior. The anterior portion is smooth, and helps to form the spheno-
maxillary fossa, while the posterior portion is rough, for articulation
with the inner surface of the pterygoid plate of the sphenoid bone.
The Internal Surface is smooth and concave, and forms part of the
outer wall of the posterior nares.
The Anterior Border forms the posterior margin of the spheno-pala-
tine notch.
The Posterior Border is serrated, and articulates with the inner sur-
face of the pterygoid process.
Development.—The palate bone is developed from a single centre
of ossification, which is deposited in membrane, and appears at the
junction of the vertical with the horizontal plate about the seventh or